1. Field of the Invention
This invention relates to polyvinyl alcohol compositions, and more particularly, to melt extrudable polyvinyl alcohol compositions containing a hydrocarbon oil or wax and either a polyethylene wax or an ethylene polymer and optionally, a plasticizer.
2. Description of the Prior Art
In extruding polyvinyl alcohol several problems have been generally encountered. The melting point of polyvinyl alcohol increases as the degree of hydrolysis increases. The polyvinyl alcohol also has a tendency to stick, thereby interfering with smooth extrusion. In order to maintain sufficient fluidity the temperature of extrusion has to be increased, which in turn results in discoloration of the extruded product. The extrudability of polyvinyl alcohol has hitherto been sought to be improved, e.g., by the addition of 5-13 weight percent polyhydric alcohol plasticizer (such as glycerine) and 0.2 weight percent stearic acid lubricant (see U.S. Pat. No. 3,607,812). While these additives, almost entirely as a result of the use of the plasticizer, render the polyvinyl alcohol somewhat more fluid, the improvement is of limited utility because of the fugitive nature of the plasticizer and the higher water sensitivity of the extruded product.